C-reactive protein (CRP) is an acute phase protein of hepatic origin in man whose plasma concentration increases markedly in response to a wide variety of inflammatory stimuli. CRP is a binding protein which, when bound to one of its ligands, has been found capable of activating complement, and affecting the function of phagocytic cells. CRP also contains tuftsin-like peptides and proteolytic fragments of CRP can stimulate inflammatory cells. These properties along with evolutionary conservation of the protein (which is even found in some invertebrates), have been interpreted as indicating that CRP functions to modulate the inflammatory response. The mouse, in contrast to most vertebrates, does not synthesize a significant quantity of CRP in response to inflammatory stimuli. We have taken advantage of this evolutionary oddity and produced transgenic mice capable of expressing rabbit CRP in order to define the functional role of CRP in vivo. These animals will be employed to assess the effects of rabbit CRP in three established mouse models of inflammation. We will: 1) Initially characterize the properties of CRP in our established transgenic mouse lines. 2) Determine the pathophysiologic and morphologic effects of transgenic CRP on endotoxic shock, antigen-induced acute arthritis and Lactobacillus induced carditis in these animals. 3) Test the in vivo importance of the phosphorylcholine (PC) binding domain of CRP since PC is a ubiquitous substrate to which CRP binds avidly. This domain will be altered by site directed mutagenesis of the rabbit CRP gene and, after confirmation that these mutants are unable to bind PC (following expression in transfected cell lines), will be employed to produce additional transgenic mice. The effects of altering the PC binding domain on the functional properties of CRP will be tested in the models outlined in 1) and 2) above.